Two valuation questions in one survey: is it a recipe for sequencing and instrument context effects?

Economic theory suggests that willingness to pay for two goods independentl y offered should remain unchanged when the survey instrument changes slight ly. Four survey treatments consisting of comprehensive good and a subset of that good were used. The surveys alternated in the question ordering and i n the embedded good which accompanied the comprehensive good. We tested for sequencing and instrument context effects using both a combined and split sample designs. In the combined sample case we found some evidence to seque ncing effects in the data containing the first subset good. Likelihood rati o tests indicated that sequencing did not effect scale or location of param eters. In the test for instrument context effects, evidence was found indic ating context does effect willingness to pay estimates.